This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:                3GPP third generation partnership project        ABSF almost blank subframe        ACK acknowledgment        BLER block error ratio or rate        DL downlink (network towards UE)        eNB EUTRAN Node B (also eNodeB)        EUTRAN evolved UTRAN (also known as LTE or LTE-A)        HARQ hybrid automatic repeat request        LTE/-A long term evolution/long term evolution-advanced        MME mobility management entity        NACK negative acknowledgment        Node B base station        PCell primary cell/primary component carrier        PDCCH physical downlink control channel        PDSCH physical downlink shared channel        PHICH physical HARQ indicator channel        PUCCH physical uplink control channel        PUSCH physical uplink shared channel        RF radio frequency        RRC radio resource signaling        SCell secondary cell/secondary component carrier        UCI uplink control information        UE user equipment        UL uplink (UE towards network)        UTRAN universal terrestrial radio access network        
The LTE system is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. In the LTE and other cellular radio systems the base station (termed an eNodeB or eNB in LTE) signals on the PDCCH the time-frequency resources (physical resource blocks) on the PDSCH and PUSCH which are allocated to a mobile terminal (UE). This scheduling technique allows advanced multi-antenna techniques like precoded transmission and multiple-input/multiple-output operation for the downlink shared data channel.
LTE is a heterogeneous network (sometimes termed HetNet), in which there are access nodes apart from the traditional base stations which operate at different power levels. For example, there may be privately operated nodes sometimes termed pico or femto nodes to which the conventional (macro) eNBs can offload traffic; there may be remote radio heads or repeaters to fill coverage holes, and there may be relay nodes which operate similar to the eNB which controls them but using a subset of the eNB's radio resources assigned to the relay node by the parent eNB.
LTE-A (expected in 3GPP Release 11) implements heterogeneous networks using carrier aggregation, where two or more component carriers spanning different frequency bands are aggregated into the same system. By example, there may be five component carriers which together cover the whole system bandwidth of 100 MHz and a given UE has two of those component carriers as active for itself. Each UE always has one PCell and may have one or more SCells, which may be in the licensed spectrum or in unlicensed spectrum such as the Industrial, Scientific and Medical (ISM) band. Any given SCell may have a full set of data and control channels (e.g., backwards compatible with 3GPP Release 8) or may carry only data channels (termed an extension carrier).
In a LTE-A heterogeneous network the same UE may be communicating with a macro eNB 14 on the PCell and with a pico eNB 12 on its SCell as shown at FIG. 1. For such an inter-site implementation of carrier aggregation, multiple component carriers are transmitted from multiple sites in the downlink and multiple component carriers are transmitted to multiple sites in uplink. Inter-site carrier aggregation can provide dynamic multilayer traffic steering or offloading, enhance data rate in the overlapped coverage region of two/multiple cells or transmission points, and reduce handover overhead. Such a Macro-Pico usage is expected to be the most typical scenario when a UE is configured with two (or more) component carriers.
In case of inter-site carrier aggregation, the UE needs to transmit the UCI that is relevant to the PCell and to the SCell, for example to report the periodic channel state information of each cell, to feedback the ACKs/NACKs relating to the scheduled resources on the PDSCH of the PCell and on the PDSCH of the SCell, and to send scheduling requests. If the UE simultaneously transmits uplink control information on both carriers in the uplink (referred to as a dual-carrier UCI transmission) it may lead to high BLER of the transmitted UCI because of the UE's power limitations and also due to a large pathloss from the UE to the macro eNB. This makes it difficult to meet the guaranteed target BLER of 1% for ACK-to-NACK and of 0.1% for NACK-to-ACK transmissions.
Exemplary embodiments disclosed below are directed toward control signaling which enables the network and UE to meet the above (or other) BLER targets, particularly in a single-carrier UCI transmission scenario.